Heat exchanger assembly

ABSTRACT

A heat exchanger assembly comprises at least two heat exchanger cores arranged in parallel flow, each heat exchanger core including a plurality of tubes, fins between the tubes and opposing headers sealingly attached at each end of the tubes. A common tank is positioned between the at least two heat exchanger cores and connected to a header at one end of each heat exchanger core, and separate tanks are connected to a header at the other end of each of the at least two heat exchanger cores. The separate tanks may be inlet tanks for fluid passing into the heat exchanger assembly and the common tank may be an outlet tank for fluid passing out of the heat exchanger assembly, or the flow path may be reversed, with the common tank being an inlet tank and the separate tanks being outlet tanks. A method for operating the heat exchanger comprises providing fluid ports on each of the common tank and the separate tanks for passage of a fluid into and out of the heat exchanger, and flowing the fluid between the common tank and the separate tanks through the at least two heat exchanger cores to cool the fluid.

RELATED APPLICATIONS

This application claims priority to U.S. Application No. 62/084,620,filed on Nov. 26, 2014.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat exchangers and, more particularly,to the field of ultra-large air-cooled heat exchangers used in vehiclesor industry, such as engine cooling radiators of the type used to coolthe largest Diesel-electric generator sets, giant earth-moving haultrucks used in open-pit mining, and some of the largest Diesel-electriclocomotives.

2. Description of Related Art

Engine cooling radiators used with internal combustion engines invehicles or industry are often quite large. Such radiators can be about9 feet (2.7 m) high by 9 feet (2.7 m) wide or larger, and are subject tounique problems. Industrial radiators such as these are typically ofcopper/brass soldered construction, wherein solder-coated brass tubesare pushed through holes in a stack of copper fins, which have been heldin the desired spacing in a grooved book jig, to form a core block. Thecore block is then baked in an oven to solder the tubes to the fins.Following this, the tube ends are inserted into brass headers at eachend of the core block and soldered, to form a core. The height of such acore is limited by the ability to push long, thin tubes through theholes in the fins, with 48 in. (1.22 m) being close to a practicalmaximum. Similarly, the size of a typical book jig limits core widths toabout 48 in. (1.22 m). Since it is impossible to form radiator coreswith tubes as long as 9 feet (2.7 m), such radiators are made with amultiple of radiator cores joined together with core connecting frames.

To make, for example, a core assembly of overall size 72 in. (1.83 m) by72 in. (1.83 m), two 36 in. (91 cm) copper/brass core blocks are solderconnected side-by-side to a single common header at the top and bottomof the core blocks to produce a first core assembly. A second coreassembly is constructed with two additional core bocks and twoadditional headers. The 36-in. (91 cm) high, 72 in. (1.83 m) wide coreassemblies are then joined to a connecting filler frame by bolting, withgaskets between the filler frame and each core header, the gasketssubstantially the same as the gasket between the radiator tank and thetop header of the upper cores. The headers of the core pairs are bolted,with gaskets, to a steel inlet tank and outlet tank with a coreseparator strip between the side-by-side cores.

Typically, engine coolant enters the large top tank and flows downthrough two upper radiator cores in parallel, then through the coreconnecting frame or frames, and finally through two lower radiator coresin parallel to the bottom outlet tank. The upper and lower radiatorcores form a series flow path, that is, coolant flows first through theupper cores and then through the lower cores, with attendant pressuredrops. The coolant flow rate needed to cool such large engines is sohigh that typically the radiators are made many more rows of tubes deepthan are needed for cooling, just to be able to pass the high coolantflows without excessive pressure drop.

While stationary generator sets are not subject to transportation shockand vibration, the earth movers and locomotives certainly are. Tosurvive this environment, radiators for such service have includedresilient tube-to-header joints, such as Mesabi® grommeted cores (U.S.Pat. No. 3,391,732) and General Electric silicone bonded locomotiveradiator headers (U.S. Pat. No. 3,447,603). However, both of theseapproaches to the problem are very expensive to implement.

Moreover, the cooling systems of some locomotives consist of multiplelarge radiators which are connected into the system by valving on an “ondemand” basis. As a result, when running in cold weather on level grade,only two of up to six available radiators might be connected. Then, whenclimbing a grade, one or more of the other radiators would be connectedin order to handle the cooling load. The result is that some radiatorswould be lying idle at winter ambient temperatures well below freezingwhen, suddenly, they would be shocked with hot coolant around 190degrees Fahrenheit. Such a thermal shock would destroy the averageradiator core, therefore resilient tube-to-header joints to absorb theexpansion/contraction of the core tubes, or, alternatively, very robustconstruction of tubes and headers, is essential. Again, both are veryexpensive.

Therefore, a need exists for changes to ultra-large radiators whichwould allow the assembled cores to be made only as deep as is necessaryfor proper cooling without raising pressure drop, which would allow thecores to be made much less expensively. A further need exists for asolution to manufacturing ultra-large radiators which includes resilienttube-to-header joints in a less expensive manner.

SUMMARY OF THE INVENTION

Bearing in mind the problems and deficiencies of the prior art, it istherefore an object of the present invention to provide an improved heatexchanger assembly for ultra-large air-cooled radiators wherein thecores are as efficient or even more so than conventional ultra-largeradiator assemblies and can be made less expensively.

It is another object of the present invention to provide an improvedheat exchanger assembly whereby the assembled cores are only as deep asis necessary for proper cooling without raising pressure drop.

It is another object of the present invention to provide an improvedheat exchanger assembly whereby the coolant flow path is reduced byhalf, thereby reducing coolant pressure drop and allowing the radiatorcores to be made thinner, with fewer of rows deep, for the same coolantpressure drop.

A further object of the invention is to provide an improved heatexchanger assembly for ultra-large radiators wherein the assemblyutilizes automotive-type CAB (controlled atmosphere brazing) plastictank aluminum core radiators instead of conventional copper/brassradiator core construction.

It is yet another object of the present invention to provide an improvedheat exchanger assembly for ultra-large radiators wherein the assemblyincludes resilient tube-to-header joints required for protection againsttransportation shock and vibration.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The above and other objects, which will be apparent to those skilled inthe art, are achieved in the present invention which is directed to, ina first aspect, a heat exchanger assembly comprising at least two heatexchanger cores arranged in parallel flow, each heat exchanger coreincluding a plurality of tubes, fins between the tubes and opposingheaders sealingly attached at each end of the tubes. The assemblycomprises a common tank between the at least two heat exchanger cores,the common tank connected to a header at one end of each heat exchangercore, and separate tanks connected to a header at the other end of eachof the at least two heat exchanger cores. The separate tanks may beinlet tanks for fluid passing into the heat exchanger assembly and thecommon tank may be an outlet tank for fluid passing out of the heatexchanger assembly, or the flow path may be reversed, with the commontank being an inlet tank and the separate tanks being outlet tanks.

The common tank may be centered between the at least two heat exchangercores, and each of the at least two heat exchanger cores may have thesame dimensions. The heat exchanger assembly may include a plurality ofheat exchanger cores and there may be the same number of heat exchangercores on each side of the common tank.

Each of the heat exchanger cores may be a copper/brass core, wherein thecommon tank and separate tanks are comprised of steel, the headers areeach comprised of brass, and the heat exchanger cores comprise brasstubes and copper or copper alloy fins.

The heat exchanger assembly may include a pair of opposing side membersadapted to provide structural support to the heat exchanger cores and tosubstantially eliminate air flow bypass around the side of the cores.The heat exchanger cores may be arranged in pairs and the heat exchangerassembly may further include a core support member disposed between eachpair of heat exchanger cores and shaped to force entering air to eitherside of the core support member and direct air flow to the fins andtubes of the heat exchanger cores. The core support member may have alength corresponding to a length of the heat exchanger cores, and awidth corresponding to a depth of the heat exchanger cores.

Each tube may have a tube end sealingly inserted into one of a pluralityof openings in the header to form a resilient tube-to-header joint.

In another aspect, the present invention is directed to a heat exchangerassembly, comprising at least two heat exchangers arranged in parallelflow, each heat exchanger including a plurality of tubes, fins betweenthe tubes, opposing headers sealingly attached at each end of the tubes,and inlet and outlet tanks sealingly attached to the headers. Theassembly comprises a common tank between the at least two heatexchangers, the common tank connected to a tank at one end of each heatexchanger, and separate tanks connected to a tank at the other end ofeach of the at least two heat exchangers. The separate tanks may beinlet tanks for fluid passing into the heat exchanger assembly and thecommon tank may be an outlet tank for fluid passing out of the heatexchanger assembly, or the flow path may be reversed, with the commontank being an inlet tank and the separate tanks being outlet tanks.

Each of the heat exchangers may be sealingly connected to the common andseparate tanks using at least one hose attached between the tank on oneend of each heat exchanger and the common tank, and the tank on theother end of each heat exchanger and one of the separate tanks,respectively.

The common tank may be centered between the at least two heatexchangers, and each of the at least two heat exchangers may have thesame dimensions. The heat exchanger assembly may include a plurality ofheat exchangers and there may be the same number of heat exchangers oneach side of the common tank.

The common tank and separate tanks may each be comprised of steel, andeach of the heat exchangers may comprise a CAB aluminum core, whereinthe tanks are comprised of plastic, and the cores comprise aluminumtubes, fins and headers.

The heat exchanger assembly may include a pair of opposing side membersadapted to provide structural support to the heat exchangers and tosubstantially eliminate air flow bypass around the side of the heatexchangers. The heat exchangers may be arranged in pairs and the heatexchanger assembly may further include a support member disposed betweeneach pair of heat exchangers and shaped to force entering air to eitherside of the support member and direct air flow to the fins and tubes ofthe heat exchangers. The support member may have a length correspondingto a length of the heat exchangers, and a width corresponding to a depthof the heat exchangers.

Each tube may have a tube end sealingly inserted into one of a pluralityof openings in the header to form a resilient tube-to-header joint.

In yet another aspect, the present invention is directed to a method ofoperating a heat exchanger. The method comprises the steps of providingat least two heat exchanger cores arranged in parallel flow, each heatexchanger core including a plurality of tubes, fins between the tubesand opposing headers sealingly attached at each end of the tubes;providing a common tank between the at least two heat exchanger cores,the common tank connected to a header at one end of each heat exchangercore; and providing separate tanks connected to a header at the otherend of each of the at least two heat exchanger cores. The method furthercomprises providing fluid ports on each of the common tank and theseparate tanks for passage of a fluid into and out of the heatexchanger, whereby one of the common tank or the separate tanks is anoutlet tank for fluid passing out of the heat exchanger and the other ofthe common tank or the separate tanks is an inlet tank for fluid passinginto the heat exchanger; and flowing the fluid between the common tankand the separate tanks through the at least two heat exchanger cores tocool the fluid.

The method may include providing each of the separate tanks with aninlet fluid port and the common tank with an outlet fluid port. In atleast one method, the step of flowing the fluid between the common tankand the separate tanks comprises first flowing the fluid through theseparate tank inlet fluid ports, through the at least two heat exchangercores, and then through the common tank outlet fluid port.

The method may further comprise the step of connecting an inlet fluidline to a fluid port on one of the common tank and the separate tanks,and connecting an outlet fluid line to a fluid port on the other of thecommon tank and the separate tanks.

In still yet another aspect, the present invention is directed to a tankfor a heat exchanger assembly, the tank positioned between at least twoheat exchanger cores each including a plurality of tubes, fins betweenthe tubes and opposing headers sealingly attached at each end of thetubes, the tank connected to a header at one end of each heat exchangercore and including a fluid port for passage of a fluid into or out ofthe heat exchanger assembly. The at least two heat exchanger cores maybe arranged in parallel flow, and the fluid may be flowed between thecommon tank and a pair of opposing separate tanks connected to a headerat the other end of each of the at least two heat exchanger coresthrough the at least two heat exchanger cores to cool the fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elementscharacteristic of the invention are set forth with particularity in theappended claims. The figures are for illustration purposes only and arenot drawn to scale. The invention itself, however, both as toorganization and method of operation, may best be understood byreference to the detailed description which follows taken in conjunctionwith the accompanying drawings in which:

FIG. 1 depicts a front elevational view of a typical modular heatexchanger assembly of the prior art, with a partial cutaway of aradiator core showing core tubes and cooling fins therebetween and thedirection of coolant flow through the assembly.

FIG. 2 depicts a front elevational view of one embodiment of a modularheat exchanger assembly according to the present invention.

FIG. 3 depicts a front elevational view of another embodiment of amodular heat exchanger assembly according to the present invention,wherein the radiator cores are automotive-type plastic tank aluminumradiators.

FIG. 4A depicts a front elevational view of an embodiment of the presentinvention wherein the modular heat exchanger assembly includes a pair ofradiator cores.

FIG. 4B depicts a front elevational view of an embodiment of the presentinvention wherein the modular heat exchanger assembly includes sixradiator cores arranged in parallel flow.

FIG. 5 depicts a cutaway view of a segment of a modular heat exchangerassembly according to the present invention shown in FIG. 2, showingheat exchanger core fins and tubes secured in headers on either side ofa common tank, with a core support member disposed between verticallyadjacent cores.

FIG. 6 depicts a cross-sectional view of a segment of an exemplaryheader according to an embodiment of the present invention, wherein eachtube-to-header joint is sealed with a resilient O-ring seal.

DESCRIPTION OF THE EMBODIMENT(S)

In describing the embodiments of the present invention, reference willbe made herein to FIGS. 1-6 of the drawings in which like numerals referto like features of the invention.

The present invention is directed to a unique assembly of radiator coreswhich cut the length of the coolant flow path by half by having thecoolant enter the radiator through two side inlet tanks and flowhorizontally through two (or more) radiator cores in parallel to acenter outlet tank. With the pressure drop thus reduced, the radiatorcores may now be made with fewer rows of tubes deep, thereby making thecores thinner and less expensive.

Certain terminology is used herein for convenience only and is not to betaken as a limitation of the invention. For example, words such as“upper,” “lower,” “left,” “right,” “horizontal,” “vertical,” “upward,”and “downward” merely describe the configuration shown in the drawings.For purposes of clarity, the same reference numbers may be used in thedrawings to identify similar elements.

Referring now to FIG. 1, a typical modular heat exchanger assembly ofthe prior art is shown. The modular heat exchanger includes a pluralityof radiator or other heat exchanger cores 10 integrally connected to aplurality of radiator tanks 71. Tanks 71A and 71C may be a single inlettank and tanks 71B and 71D may be a single outlet tank. The coresinclude parallel vertical tubes 20 and fins 30 between the tubes forincreased heat exchange efficiency, and may be CAB (controlledatmosphere brazing) aluminum cores. The cores 10 each include a firstheader 16A at the top end of the core and a second header 16B at thebottom end of the core. The modular heat exchanger shown includes fouridentical cores 10A, 10B, 100, 10D. Vertically adjacent cores 10A, 10Bare connected such that the bottom header 16B of core 10A is sealinglyconnected with the top header 16A of core 10B using a filler frame orconnector member 12A. Likewise, vertically adjacent cores 10C, 10D areconnected using a similar filler frame or connector member 12B securedbetween bottom header 16B of core 10C and top header 16A of core 10D.The filler frame or connector member 12A, 12B is an elongated memberhaving a length approximately equal to the width of the cores and awidth approximately equal to the depth of the cores. The length of thefiller frame is typically greater than the width. An opening on the topand bottom of filler frame member 12A, 12B permits passage of coolantbetween the vertically connected cores, and the filler frame member mayinclude a laterally outwardly extending top foot or lip and a laterallyoutwardly extending bottom foot or lip along the perimeter of each ofthe openings to permit the filler frame member to be sealingly securedwith gaskets to the headers of each of the cores. The filler framemembers may be made of any suitable material, for example steel.

Each heat exchanger header 16A, 16B, 16C, 16D may be sealingly connectedwith a gasket to the filler frame 12 or the tank 71 in accordance withknown methods such as bolting.

The modular heat exchanger assembly of the prior art further includesupper radiator or coolant tanks 71A, 71C sealingly connected to the topheader 16A of cores 10A, 10C, respectively, and lower radiator orcoolant tanks 71B, 71D sealingly connected to the bottom header 16B ofcores 10B, 10D, respectively. The tanks 71 each have an inlet/outlet 81for connection to an internal combustion engine or other externalsystem. Tanks 71 may be made of any suitable material, such as steel.Structural side members 40 are provided and are disposed adjacent heatexchanger cores along the left and right side of the modular heatexchanger and are used to protect and support the core sides and tosubstantially eliminate air flow bypass around the sides of the cores.An elongated core support member 50 performs a similar task as thestructural side members 40 and extends between upper and lower headersof the cores.

Typically, coolant enters the top inlet tanks 71A, 71C and flows downthrough the two upper radiator cores 10A, 10C in parallel, through thefiller frame or connector member 12A, 12B, and finally through the twolower radiator cores 10B, 10D in parallel to the outlet tanks 71B, 71D.The upper and lower radiator cores form a series flow path, that is,coolant flows first through the upper cores and then through the lowercores, with attendant pressure drops. The coolant flow rate needed tocool such large engines is so high that typically the radiators are mademany more rows of tubes deep than are needed for cooling, just to beable to pass the high coolant flows without excessive pressure drop.

U.S. Pat. No. 8,631,859, entitled “Modular Heat Exchanger”, shows inFIG. 9 a modular heat exchanger assembly made up of CAB aluminumradiator cores crimped to plastic tanks which are, in turn, sealinglyconnected to metal heat exchanger assembly tanks. It also shows, in FIG.2, a modular heat exchanger assembly made up of CAB aluminum radiatorcores crimped to plastic heat exchanger assembly tanks. In both cases,fluid flows in series, with high attendant pressure drop, first throughthe upper radiator cores and then through the lower radiator cores. Themodular heat exchanger assembly of the present invention remedies thisdeficiency by reducing the coolant flow path by half, thereby reducingthe coolant pressure drop and allowing the radiator cores to be madethinner, with fewer rows of tubes deep, for the same coolant pressuredrop. This reduction in core depth will result in significantmanufacturing time and cost savings.

Referring now to FIG. 2, one embodiment of the modular heat exchangerassembly of the present invention is shown. The modular heat exchangerincludes at least two radiator or other heat exchanger cores 100arranged in parallel flow and integrally connected to a plurality ofradiator tanks 710. For clarity, cooling air bypass shields and mountingstructure have been omitted in all Figures. The cores include aplurality of parallel tubes 20 and fins 30 between the tubes forincreased heat exchange efficiency, and may be comprised of conventionalcopper/brass soldered construction, copper/brass brazed construction(CuproBraze®) or CAB (controlled atmosphere brazing) aluminumconstruction. As shown in FIG. 2, the cores are comprised ofconventional copper/brass soldered construction, as described above. Thecores 100 each include a first header 160A sealingly attached at one endof the core tubes and a second header 160B sealingly attached at theopposite end of the core tubes. Each header 160A may be an inlet headerfor passage of coolant into the modular heat exchanger assembly, and thecores may be positioned such that coolant will flow through the coretubes in a horizontal direction between the headers 160A, 160B.

The modular heat exchanger shown in FIG. 2 includes fouridentically-dimensioned cores 100A, 100B, 100C, 100D. Verticallyadjacent cores 100A, 100B are separated by a core support member 500disposed therebetween. Support member 500 is used to protect and supportthe core sides and to substantially eliminate air flow bypass around thesides of the cores. Likewise, vertically adjacent cores 100C, 100D areconnected using a similar core support member 500 disposed between cores100C, 100D. The core support member 500 is an elongated member having alength approximately equal to the length of the cores and a width (inthe direction of air flow, into the Figure) approximately equal to thedepth of the cores. The core support members may be made of any suitablematerial, for example steel or aluminum, and are shaped to forceentering air to either side of the core support member and direct airflow to the fins and tubes of the heat exchanger cores.

The modular heat exchanger assembly of the present invention includesseparate radiator or coolant tanks 710A, 710C on either side of theassembly sealingly connected to the first headers 160A of cores 100A,100B, 100C, 100D, respectively, and a common tank 710B disposed betweenand sealingly connected to the second headers 160B of cores 100A, 100B,100C, 100D, respectively. Common tank 710B may be centered between oneor more pairs of horizontally adjacent cores, as shown in FIG. 2. Thetanks 710 each have an inlet/outlet for connection to an internalcombustion engine or other external system.

Inlet/outlet fluid ports 810 are provided on each of the common tank710B and the separate tanks 701A, 710C for passage of fluid into and outof the heat exchanger. In an embodiment, the separate tanks may be inlettanks for fluid passing into the heat exchanger assembly and the commontank may be an outlet tank for fluid passing out of the heat exchangerassembly, or the flow path may be reversed, with the common tank beingan inlet tank and the separate tanks being outlet tanks. In operation,fluid enters the assembly through inlet ports in either the common tankor separate tanks, and the fluid flows between the common tank and theseparate tanks, respectively, through the at least two heat exchangercores to cool the fluid. By cutting the length of the coolant flow pathin half over that of the conventional prior art modular assembly, thecoolant pressure drop is reduced, allowing the radiator cores to be madethinner, with fewer rows of tubes deep, for the same coolant pressuredrop. In certain embodiments, the radiator cores may be as few as asingle row of tubes deep depending on design requirements.

As shown in FIG. 2, in at least one embodiment, heated coolant entersthe heat exchanger assembly through inlet fluid ports 810 in side,opposing coolant tanks 710A, 710C and flows horizontally in parallelflow through a plurality of tubes in the horizontally adjacent radiatorcores to a center, common outlet tank 710B which includes an outletfluid port 810. Coolant does not flow through core support member 500.It should be understood by those skilled in the art that in accordancewith the objects of the present invention, in alternate embodiments thedirection of coolant flow may be reversed, e.g. the common tank 710B maybe an inlet tank and the side tanks 710A, 710C may be outlet tanks.Tanks 710 may be made of any suitable material, such as steel.Structural side members 400 are provided and are disposed adjacent theheat exchanger cores along the sides of the modular heat exchangerassembly which do not include coolant tanks and are used to protect andsupport the core sides, provide for mounting attachments, and tosubstantially eliminate air flow bypass around the sides of the cores.

FIG. 5 depicts a cutaway view of a segment of an embodiment of themodular heat exchanger assembly of the present invention shown in FIG.2, showing heat exchanger core fins and tubes secured in headers oneither side of a common tank, with a core support member disposedbetween vertically adjacent cores. As shown in FIG. 5, a common tank710B is centered between horizontally adjacent cores 100A, 100C and100B, 100D, respectively. Tank 710B may be an outlet tank and mayinclude a plurality of integral outlet headers 160B on either side ofthe tank. A plurality of core tubes 20 are secured in openings in theheader 160B wall, with fins 30 positioned between the tubes forincreased heat exchange efficiency. Coolant flows in a parallel flowbetween the separate tanks (not shown) and the common tank 710B throughthe heat exchanger cores 100A, 100B, 100C, 100D to cool the coolant.

As shown in FIG. 5, in at least one embodiment, heated coolant flowshorizontally through the plurality of tubes 20 in each core in parallelflow, through outlet headers 160B and into outlet tank 710B beforeexiting the tank through an outlet fluid port (not shown). Core supportmember 500 is disposed between vertically adjacent cores 100A, 100B and100C, 100D, respectively, and is shaped to force entering air to eitherside of the core support member and direct air flow to the fins andtubes of the heat exchanger cores. Coolant does not pass through thecore support member 500.

The modular assembly of the present invention may be applied to any typeof radiator core construction, including the conventional large,multi-cored copper/brass core assembly construction, as shown in FIG. 2.However, such a large core assembly of copper/brass material isexpensive for two reasons. First, the price of copper and copper-basedalloys is expensive and, second, the manufacturing methods associatedwith soldered or brazed copper/brass radiator construction arelabor-intensive.

Automobile and light truck, and some heavy truck, radiators have longsince abandoned costly copper/brass radiator construction in favor ofCAB (controlled atmosphere brazing) aluminum core construction withplastic tanks. PTA (plastic tank aluminum) radiators have tabbedaluminum headers which are crimped to a plastic radiator tank with anelastomeric gasket between. This type of construction is more automated,requires far less labor, is more consistent, uses less costly material,and results in a product which is lighter, stronger and which hasdemonstrated improved durability compared to soldered copper/brass.However, the available CAB furnaces limit core size to not larger thanabout 48 inches square.

Referring now to FIG. 3, another embodiment of the modular heatexchanger assembly of the present invention is shown, wherein theassembly utilizes modern automotive-type radiators of PTA (plastic tankaluminum) core construction, as opposed to a conventional copper/brasscore assembly construction typically used in large industrial orvehicular radiators. FIG. 3 is a front elevational view of the assembledmodular heat exchanger which includes a plurality of radiators or otherheat exchangers 1000 of PTA core construction integrally connected to aplurality of steel tanks 7100 and arranged in a similar manner to theembodiment shown in FIG. 2. For clarity, cooling air bypass shields andmounting structure have been omitted. The individual inlet/outlet tanks1600 of each radiator or heat exchanger are connected to side inlettanks 7100A, 7100C and common outlet tank 7100B, respectively, by meansof one or more hoses 600. As shown in FIG. 3, radiator tanks 1600A areinlet tanks including headers (not shown) for passage of fluid into theradiators, whereas radiator tanks 1600B are outlet tanks and includeheaders (not shown) for passage of fluid out of the radiators and intothe radiator outlet tanks 7100B. As described above, in at least oneembodiment, coolant enters the heat exchanger assembly through inlets810 in side, opposing coolant tanks 7100A, 7100C, flows through theplurality of hoses 600 into radiator inlet tanks 1600A and then flowshorizontally in parallel flow through a plurality of tubes 20 inhorizontally adjacent radiators or heat exchangers 1000, throughradiator outlet tanks 1600B to a common outlet tank 7100B by way of oneor more hoses 600. Again, it should be understood by those skilled inthe art that in accordance with the objects of the present invention thedirection of coolant flow may be reversed. The headers (not shown) ofeach radiator or heat exchanger 1000 may be sealingly interconnected tothe respective inlet/outlet tanks 1600.

In a typical PTA core construction, the core tubes and fins are made ofaluminum or an aluminum alloy, and may be clad or coated with brazematerial, but other metals and alloys may also be used. The tubes areinserted into, and sealed to, openings in the walls of an aluminum inletheader and outlet header, respectively, to make up the core. The headersare connected to, or part of, plastic inlet and outlet tanks ormanifolds and structural side pieces connect the tanks to complete theheat exchanger. Each of the tubes has a tube end secured in an openingin the header wall to form a tube-to-header joint. Oval tubes aretypically utilized for close tube spacing for optimum heat transferperformance of the heat exchanger, although other tube shapes andcross-sections may be utilized. The tube-to-header joint is typicallybrazed to prevent leakage around the tubes and header.

Rigid tube-to-header joints pose several problems in the field ofultra-large heat exchangers, for example, while stationary generatorsets are not subject to transportation shock and vibration, earth moversand locomotives certainly are. This transportation shock and/orvibration can lead to failure at the tube-to-header joint, destroyingthe radiator core. Moreover, the cooling systems of some locomotivesconsist of multiple large radiators which are connected into the systemby valving on an “on demand” basis. As a result, when running in coldweather on level grade, only two of up to six available radiators mightbe connected. Then, when climbing a grade, one or more of the otherradiators would be connected in order to handle the cooling load. Theresult is that some radiators would be lying idle at winter ambienttemperatures well below freezing when, suddenly, they would be shockedwith hot coolant around 190 degrees Fahrenheit. Such a thermal shockwould destroy the average radiator core; therefore, resilienttube-to-header joints to absorb the expansion/contraction of the coretubes are essential.

The modular heat exchanger assembly of the present invention remediesthese deficiencies by, in at least one embodiment, utilizing a resilientO-ring seal which does not require brazing at the tube-to-header jointand allows for relative motion between the tube and header without thebuild-up of high stresses. FIG. 6 depicts a cross-sectional view of asegment of an exemplary header according to an embodiment of the presentinvention, wherein each tube-to-header joint is sealed with a resilientO-ring seal. As shown in FIG. 6, in at least one embodiment, each header160A, 160B may be comprised of producing by stamping two mating headerplates 302, 304. Each header plate includes a plurality of clearanceholes 306 for heat exchanger core tubes 20 to pass through, and aroundeach clearance hole is a continuous depression 308 forming one half ofan O-ring groove 318. O-rings 310 are assembled into these depressions,and the mating header plate is placed on top of the lower plate andsecured, such as by spot-welding at location 314, thereby trapping theO-rings in their O-ring grooves 318. As shown in FIG. 6, the O-rings 310are assembled in a thin sheet 320 which is sealed between the matingheader plates 302, 304 during assembly of the header 160A, 160B. Inother embodiments, the O-rings may be assembled to the header plate 302individually, rather than in one or more O-ring sheets. The assembledheader 160A, 160B is then slid over the tube ends 112 of the heatexchanger core 100A, 100B, 100C, 100D to its required location, eithermanually or through automation. After the header is fitted over the tubeends, the tubes 20 are then expanded internally by mandrels to providethe necessary O-ring deformation required to obtain a seal 312. Inservice, the resiliency of the O-ring seal 312 allows for expansion andcontraction of the tubes without the build-up of high stresses at thetube-to-header joint. The connection and method for connection of suchtube-to-header joints are also described in U.S. patent application Ser.No. 14/844,553 entitled “Heat Exchanger Tube-to-Header Sealing System”,the disclosure of which is hereby incorporated by reference. Theassembled headers 160 may then be sealingly interconnected to thecoolant tanks 710, as shown in FIG. 2. This resilient tube-to-headersealing system may also be used with the PTA (plastic tank aluminum)heat exchanger construction shown in FIG. 3.

The modular heat exchanger assembly according to the present inventionis applicable to many types of ultra-large air-cooled heat exchangers,such as radiators, charge air coolers and air cooled oil coolers, foruse in vehicles or industry. The assembly may include any number of heatexchanger cores arranged in parallel flow. The cores shown in FIGS. 2and 3 are in a 2×2 row and column arrangement. If each core were 36 in.(0.91 m) high×36 in. (0.91 m) wide, the final modular heat exchangerassembly would be about 72 in. (1.83 m) high (plus the height of theside support members and center core support member)×72 in. (1.83 m)wide (plus the width of the inlet tanks and common outlet tank). Itshould be understood by those in the art that additional rows or columnsmay be provided, as in 1×2 (FIG. 4A), 3×2 (FIG. 4B), 4×2 or morearrangements to use smaller individual core sizes, or to create largermodular cores.

Thus the present invention achieves one or more of the followingadvantages. The present invention provides an improved modular heatexchanger assembly which reduces the coolant flow path length by half,thereby reducing coolant pressure drop and allowing the radiator coresto be made thinner, with fewer rows of tubes deep, for the same coolantpressure drop. The assembly is applicable to all types of heat exchangercore construction, and can provide significant cost reductions overconventional practice by utilizing automotive-type PTA core radiatorsconnected in parallel to inlet side tanks and a center outlet tank bymeans of hoses. The assembly may include resilient tube-to-header jointswhich will provide protection against thermal shock in some locomotiveand other radiator applications, at a greatly reduced cost. The assemblycan also be applied to various ultra-large heat exchangers, such asradiators, charge air coolers and air cooled oil coolers.

While the present invention has been particularly described, inconjunction with specific embodiments, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

Thus, having described the invention, what is claimed is:
 1. A heatexchanger assembly, comprising: at least two heat exchanger coresarranged in parallel flow, each heat exchanger core including aplurality of tubes, fins between the tubes and opposing headerssealingly attached at each end of the tubes; a common tank between theat least two heat exchanger cores, the common tank connected to a headerat one end of each heat exchanger core; and separate tanks connected toa header at the other end of each of the at least two heat exchangercores, whereby one of the common tank or the separate tanks is an outlettank or tanks for fluid passing out of the heat exchanger assembly andthe other of the common tank or the separate tanks is an inlet tank ortanks for fluid passing into the heat exchanger assembly.
 2. The heatexchanger assembly of claim 1 wherein the common tank is centeredbetween the at least two heat exchanger cores.
 3. The heat exchangerassembly of claim 1 including a plurality of heat exchanger cores andwherein there are the same number of heat exchanger cores on each sideof the common tank.
 4. The heat exchanger assembly of claim 1 whereinthe common tank and separate tanks are each comprised of steel, theheaders are each comprised of brass, and the heat exchanger corescomprise brass tubes and copper or copper alloy fins.
 5. The heatexchanger assembly of claim 1 including a pair of opposing side membersadapted to provide structural support to the heat exchanger cores and tosubstantially eliminate air flow bypass around the side of the cores. 6.The heat exchanger assembly of claim 1 wherein the heat exchanger coresare arranged in pairs and further including a core support memberdisposed between each pair of heat exchanger cores and shaped to forceentering air to either side of the core support member and direct airflow to the fins and tubes of the heat exchanger cores.
 7. The heatexchanger assembly of claim 1 wherein each tube has a tube end sealinglyinserted into one of a plurality of openings in the header to form aresilient tube-to-header joint.
 8. A heat exchanger assembly,comprising: at least two heat exchangers arranged in parallel flow, eachheat exchanger including a plurality of tubes, fins between the tubes,opposing headers sealingly attached at each end of the tubes, and inletand outlet tanks sealingly attached to the headers; a common tankbetween the at least two heat exchangers, the common tank connected to atank at one end of each heat exchanger; and separate tanks connected toa tank at the other end of each of the at least two heat exchangers,whereby one of the common tank or the separate tanks is an outlet tankor tanks for fluid passing out of the heat exchanger assembly and theother of the common tank or the separate tanks is an inlet tank or tanksfor fluid passing into the heat exchanger assembly.
 9. The heatexchanger of claim 8 wherein the heat exchangers are sealingly connectedto the common and separate tanks using at least one hose attachedbetween the tank on one end of each heat exchanger and the common tank,and the tank on the other end of each heat exchanger and one of theseparate tanks, respectively.
 10. The heat exchanger assembly of claim 8wherein the common tank is centered between the at least two heatexchangers.
 11. The heat exchanger assembly of claim 8 including aplurality of heat exchangers and wherein there are the same number ofheat exchangers on each side of the common tank.
 12. The heat exchangerassembly of claim 10 wherein the common tank and separate tanks are eachcomprised of steel and each of the heat exchangers comprises a CABaluminum core, wherein the tanks are comprised of plastic and the coresare comprised of aluminum tubes, fins and headers.
 13. The heatexchanger assembly of claim 10 including a pair of opposing side membersadapted to provide structural support to the heat exchangers and tosubstantially eliminate air flow bypass around the side of the heatexchangers.
 14. The heat exchanger assembly of claim 10 wherein the heatexchangers are arranged in pairs and further including a support memberdisposed between each pair of heat exchangers and shaped to forceentering air to either side of the support member and direct air flow tothe fins and tubes of the heat exchangers.
 15. The heat exchangerassembly of claim 10 wherein each tube has a tube end sealingly insertedinto one of a plurality of openings in the header to form a resilienttube-to-header joint.
 16. A method of operating a heat exchanger,comprising the steps of: providing at least two heat exchanger coresarranged in parallel flow, each heat exchanger core including aplurality of tubes, fins between the tubes and opposing headerssealingly attached at each end of the tubes; providing a common tankbetween the at least two heat exchanger cores, the common tank connectedto a header at one end of each heat exchanger core; providing separatetanks connected to a header at the other end of each of the at least twoheat exchanger cores; providing fluid ports on each of the common tankand the separate tanks for passage of a fluid into and out of the heatexchanger, whereby one of the common tank or the separate tanks is anoutlet tank or tanks for fluid passing out of the heat exchanger and theother of the common tank or the separate tanks is an inlet tank or tanksfor fluid passing into the heat exchanger; and flowing the fluid betweenthe common tank and the separate tanks through the at least two heatexchanger cores to cool the fluid.
 17. The method of claim 16 whereineach of the separate tanks includes an inlet fluid port and the commontank includes an outlet fluid port, and wherein the step of flowing thefluid between the common tank and the separate tanks comprises firstflowing the fluid through the separate tank inlet fluid ports, throughthe at least two heat exchanger cores, and then through the common tankoutlet fluid port.
 18. The method of claim 16 further comprising thestep of connecting an inlet fluid line to a fluid port on one of thecommon tank and the separate tanks, and connecting an outlet fluid lineto a fluid port on the other of the common tank and the separate tanks.19. A tank for a heat exchanger assembly, the tank positioned between atleast two heat exchanger cores each including a plurality of tubes, finsbetween the tubes and opposing headers sealingly attached at each end ofthe tubes, the tank connected to a header at one end of each heatexchanger core and including a fluid port for passage of a fluid into orout of the heat exchanger assembly.
 20. The tank of claim 19 wherein theat least two heat exchanger cores are arranged in parallel flow andwherein the fluid is flowed between the common tank and a pair ofopposing separate tanks connected to a header at the other end of eachof the at least two heat exchanger cores through the at least two heatexchanger cores to cool the fluid.